Formatted question description: https://leetcode.ca/all/405.html

# 405. Convert a Number to Hexadecimal

Easy

## Description

Given an integer, write an algorithm to convert it to hexadecimal. For negative integer, two s complement method is used.

Note:

1. All letters in hexadecimal (a-f) must be in lowercase.
2. The hexadecimal string must not contain extra leading 0s. If the number is zero, it is represented by a single zero character '0'; otherwise, the first character in the hexadecimal string will not be the zero character.
3. The given number is guaranteed to fit within the range of a 32-bit signed integer.
4. You must not use any method provided by the library which converts/formats the number to hex directly.

Example 1:

Input:
26

Output:
"1a"


Example 2:

Input:
-1

Output:
"ffffffff"


## Solution

First convert num into 8 parts, each of which can be represented by a hexadecimal number with length 1. Convert each part to hexadecimal and concatenate the parts. Avoid leading zeroes.

class Solution {
public String toHex(int num) {
if (num == 0)
return "0";
int[] bytes = new int;
for (int i = 0; i < 8; i++) {
int temp = (num >> 4 * i) & 0xf;
bytes[7 - i] = temp;
}
String hex = "";
boolean flag = false;
for (int i = 0; i < 8; i++) {
int curByte = bytes[i];
if (!flag && curByte == 0)
continue;
hex += hexChar(curByte);
flag = true;
}
return hex;
}

public char hexChar(int num) {
if (num < 10)
return (char) (num + '0');
else
return (char) (num - 10 + 'a');
}
}